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Doppler Effect: Surface Water Waves

Experiment #22 from Physics with Video Analysis

Education Level
High School


Have you ever noticed that when a train or car moves past you rapidly its whistle or horn seems to change to a lower note? In 1842 an Austrian Physicist, Hans Christian Doppler, asserted that sound waves emitted by a moving train would have a higher frequency when moving toward a listener and a lower frequency when moving away. For surface waves in water, Doppler predicted the same type of frequency shift. In particular, a decrease in the frequency of waves propagating behind a source that moves away at a speed vs can be predicted using the Doppler equation

{f_{\text{B}}} = {f_0}\frac{{{v_{\text{w}}}}}  {{{v_{\text{w}}} + {v_{\text{s}}}}}

where vw is the speed of wave propagation in water and f0 is the frequency of the waves created by a stationary source. Doppler also predicted that the frequency increase in front of a source is given by

{f_{\text{F}}} = {f_0}\frac{{{v_{\text{w}}}}}  {{{v_{\text{w}}} - {v_{\text{s}}}}}


In this activity, you will

  • Verify the Doppler Equations for surface waves in water by using Logger Pro to analyze two high speed movies.

Sensors and Equipment

This experiment features the following sensors and equipment. Additional equipment may be required.

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This experiment is #22 of Physics with Video Analysis. The experiment in the book includes student instructions as well as instructor information for set up, helpful hints, and sample graphs and data.

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